A 70-year-old woman was killed crossing the street in Brooklyn this morning by the driver of an MTA bus who left the scene. [UPDATE]The driver has been arrested and charged.

Police say that the woman was walking north across Fulton Street at Sackman Street at around 6:15 a.m. when the driver of an MTA bus turned left onto Fulton off Sackman Street and struck her.

The woman, whose name is being withheld pending family notification, was pronounced dead at the scene.

An NYPD spokesperson says that the driver of the bus has not been located, and that the investigation is ongoing.

“She was cut in half ... definitely in half,” a witness told the Daily News. “I tried to help her but she was too bloody. There was a lot of blood.”

A spokesman for the bus drivers' union, TWU Local 100, did not have an immediate comment.

After six MTA bus drivers were arrested and charged with misdemeanors for failing to exercise due care and fatally striking under the Right of Way law, TWU Local 100 sued. The City settled in September, with an addendum to the law that defines "due care" as "that care which is exercised by reasonably prudent driver."

"This is a classic right of way, due care situation, but if it was indeed a hit and run there should be much stronger charges," says Paul Steely White, the executive director of Transportation Alternatives. "If indeed this driver hit and ran and fled the scene, a due care violation is the least of their worries."

Under New York law, leaving the scene of a collision involving death is a felony.

While the intersection does not appear to have a marked crosswalk, attorney and safe streets advocate Steve Vaccaro points out that after stopping for a stop sign, the bus driver would have had to yield to any pedestrians in the unmarked crosswalk [PDF]. The intersection also lacks traffic signals, meaning that under city law, pedestrians are permitted to cross the street mid-block.

"Even if she's crossing outside of the crosswalk, she still has the right to cross," Vaccaro says.

In an email, Wiley Norvell, a spokesman for the Mayor's Office, writes, "In accordance with the NYPD's established procedure, the Collision Investigation Unit will be conducting a thorough investigation to determine whether the driver committed a violation of [the Right of Way law], as well as any other vehicular laws."

At a press conference in Greenpoint, Mayor de Blasio was asked whether his administration was doing enough to implement his Vision Zero plan, given today's fatal crash and the incident this past weekend in which a driver jumped the curb in the Bronx and killed three pedestrians, including a 10-year-old girl.

"We are absolutely committed to Vision Zero, it is showing more success than ever," the mayor replied. "Remember this is a new initiative that is deepening all the time. We're making more changes to traffic patterns and road design, the message that is being sent to people all over the city to be careful when you drive, to be mindful of the people around you is being heard more and more."

The mayor added, "And every time we lose someone we say this is something we need to keep reiterating to people, the care they need to take with driving and why all these standards matter, why that lower speed limit matters. And I think more and more people are getting it."

Additional reporting by Miranda Katz.